The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Cruise control systems are utilized on vehicles to enable the vehicle to maintain a desired vehicle speed. A controller maintains the vehicle speed through varying road and vehicle conditions. A vehicle operator may set and manipulate a cruise control target speed through depression of an accelerator pedal, a brake pedal, and/or a clutch pedal, as well as via actuation of hand controls.
When a target speed is set, cruise control systems attempt to maintain a current vehicle speed at approximately the target speed. The current vehicle speed may be different than the target vehicle speed due to various vehicle operating conditions. For example, when traveling on inclined road surfaces, the current vehicle speed may be less than or greater than the target speed.
Cruise control systems typically allow the vehicle operator to return to and/or increase a target speed by pushing a RESUME button or to set, decrease and/or reset the target speed by pushing a SET button. A calibration window is often centered about the target speed. A calibration factor is equal to half a width of the calibration window. A first target speed may be set by pushing the SET button when cruise control is active. A reset of target speed occurs when the SET button is pushed while vehicle speed is outside the calibration window.
The reset can either increase or decrease target speed. For example, the target speed is increased when the SET button is depressed and the current vehicle speed is equal to at least the target speed plus the calibration factor. Put another way, the target speed is increased when the current vehicle speed is greater than the target speed and outside the calibration window. The target speed is decreased when the current vehicle speed is greater than the target speed and inside the calibration window. Usually, the target speed is decreased by a set reduction amount through pushing of the SET button. When the SET button is depressed and the current vehicle speed is within the calibration window, the target speed is reduced.
As an example, the calibration factor may be set at 5 miles per hour (mph). When a request command signal is received to reset the target speed, the cruise control system either significantly increases or decreases the target speed, or slightly reduces the target speed such as 1 mph.
Under certain scenarios, a cruise control system may not respond to vehicle operator input as the vehicle operator intended. For instance, a vehicle operator may depress an accelerator pedal to increase the current vehicle speed to a command speed and push the SET button to reset the target speed. However, due to cruise control system operating limitations, the cruise control system may not reset the target speed at the command speed. The calibration factors are designed into cruise control systems to avoid inappropriate vehicle response, but have operating limitations.
As another example, when the calibration factor is large, a request command signal may be denied and thus a set target speed is not increased, but rather is decreased. Similarly, when the calibration factor is small, the target speed can be easily reset. A small calibration factor can result in an increase in the target speed without driver depression of an accelerator pedal, although the vehicle operator intended a decrease in the target speed.
As a further example, a vehicle when operating on a declined surface may experience a current vehicle speed that is above a target speed. The vehicle operator may attempt to reduce the target speed through depression of the SET button. However, since the current vehicle speed is greater than the target speed and outside a corresponding calibration window, the target speed may be increased.